Code Reviews
I personally believe code reviews to be one of the most valuable opportunities for professional growth when it's approached with the right mindset. Far too often, though, I see egos creep into the code review process. There is no room for ego in a code review, and you should never take a defensive stance when someone has taken the time to offer you a different solution.
I also make it a habit to participate in code reviews, even if I'm just acting as an observer. I've gained a ton of cool tricks, ideas, and core knowledge over the years directly from participating in code reviews. Everyone can learn something as part of the code review process, no matter how seasoned they are.
Greener developers tend to refrain from commenting because they lack confidence and don't want to say anything wrong. To them, I offer this advice: just go for it. Check the docs before you post it just to add a little extra confidence. If you get it wrong, so what? You'll gain a better understanding by receiving the feedback. We all have to learn somehow, so just go for it.
I try to create a strong team culture that embraces code reviews by having everyone participate. We're all busy, but we should all make code reviews a priority amongst our team. If your team isn't making code reviews a priority or is allowing egos to seep in throughout the process, talk to your team lead and be the positive example or catalyst for change. Anyone has the power to positively impact a team, so why shouldn't it be you? After all, we're a team for a reason. It takes each one of us to succeed.
A mentor comes in handy for code reviewing pet projects, which is another reason why the mentor/mentee relationship is so important. I've also found Reddit to be a great place to reach out for code reviews when I'd like some additional input on my pet projects. There are many Slack and Discord channels you can participate in that contain willing individuals who will set eyes on your code and provide feedback. IRC is also great for those in the know. Code reviews expedite growth, so don't hesitate to get creative in sourcing reviewers.